Posted
by
timothyon Friday November 19, 2010 @07:20AM
from the good-skill-to-pick-up dept.

Hugh Pickens writes "Researchers at MIT have developed a laser camera that can 'see' around corners and take pictures of a scene not in its direct line of sight. The camera system fires extremely short bursts of light that can reflect off one object, such as the open door of a room, and then off a second object inside the room before reflecting back to the first object and being captured by the camera, after which algorithms can use the information to reconstruct the hidden scene exploiting the fact that it is possible to capture light at extremely short time scales, about one quadrillionth of a second. By continuously gathering light and computing the time and distance that each pixel has traveled, the camera creates a '3D time-image' of the scene it can't directly see. 'It's like having X-ray vision without the X-rays,' says Professor Ramesh Raskar. 'We're going around the problem rather than going through it.'"

Indeed. And based on that pic, you can see (or not - no pun intended) why there wasn't a pic in the other write-ups. As the BBC article says:

At the moment, the set-up only works in controlled laboratory conditions and can get confused by complex scenes. "It looks like they are very far from handling regular scenes," said Prof Nayar. In everyday situations, he said, the system may compute "multiple solutions" for an image, largely because it relied on such small amounts of light and it was therefore difficul

You were modded funny but you should have been modded pedantic. If you really want to be pedantic you should have pointed out that in an atmosphere or other non-vacuum medium it is slower than theoretical C. Second, one foot is a very good approximation of the speed of light and perfectly suitable to use in a non-journal science article. Seriously, if you're going to nitpick like that you really need to get a life and move out of your mother's basement.

It's not, because the meter is defined by c, so in this particular case, it offers a precise value.

In 1983 the metre was defined as "the length of the path traveled by light in vacuum during a time interval of 1299,792,458 of a second", fixing the value of the speed of light at 299,792,458 m/s by definition

Yes, that's been annoying me at work. Most of the links are firewalled off, but I can usually find a better FA with Google. With dozens or hundreds of stories written by professionals and posted on sites that can handle a slashdotting, why do these stories link to some blog that merely quotes a mainstream news source, is firewalled off in many places, and is frequently slashdotted to oblivion?

Firehosers, I'm calling on you all to turn these down. I'll bet there were half a dozen submissions of this same sto

It would make a helluva lot more sense to just use high-intensity microwaves. Think of how Dolphins and bats see their environment. the device to see around corners would have to take various additional factors into account of course, like distance from the reflecting surface and angle of beam contact to said surface. After that, it's just a matter of painting a 3d version of the room.:|

The process has to be incredibly time-sensitive in order to work, and the imaging process has to subtract ambient light in order to obtain the reflected-laser data. This ambient-light recording has to happen at a different time to when the laser is fired, so variable-light conditions or the lack of an incredibly steady camera, image object and reflective surface will make it basically impossible to render the image.

I absolutely love the concept. I just think that the nay-sayers whom Professor Raskar claims to be defeating were correct. It might not be theoretically impossible, but the practical limitations are so severe that I don't envisage them being "engineered" away - and if they are, such phenomenal engineering accomplishments would make this application appear trivial in comparison with the other things we could do.

Indeed, not to mention the limitation that you need a surface off of which you bounce the intitial laser pulse. This "looking round corners" idea/phrase someone has put forward is total crap. Sure, you can look around a corner as long as it's (e.g.) a doorframe and the door opens outwards in the right direction for your camera to use as a reflector. Want to look round the corner of a building? Into a room where the door opens inwards? Over a wall? Then you're shit out of luck.

If it has to be incredibly time sensitive to work why not use sound (ultra-sonic waves, like bats use) instead. This should reduce the time sensitivity requirements by many orders of magnitude. It will also reduce the resolution but considering that bats can catch insects in flight probably will still be good enough to "see" someone hiding behind a door.

Or perhaps they need a coherent (laser) beam of sound? Perhaps this can be engineered around. Might also be useful underwater.

Given that he's using a femtosecond laser and some kind of exotic "streak" camera, I think he has to essentially raster scan the area he's imaging "around the corner". I doubt the ambient lighting or the scene itself will change in a femtosecond, but the raster-scanner better move pretty fast! A fast raster-scanner might be solvable, even. I think the biggest problem he's going to have is dealing with a non-sparse scene. I think this works well for simple geometries, but once he starts dealing with a re

This ambient-light recording has to happen at a different time to when the laser is fired, so variable-light conditions or the lack of an incredibly steady camera, image object and reflective surface will make it basically impossible to render the image.

Yeah but you could record the ambient light 1 ms later. Light is pretty damn fast and ambient light conditions are essentially constant.

I absolutely love the concept. I just think that the nay-sayers whom Professor Raskar claims to be defeating were correct. It might not be theoretically impossible, but the practical limitations are so severe that I don't envisage them being "engineered" away - and if they are, such phenomenal engineering accomplishments would make this application appear trivial in comparison with the other things we could do.

I wouldn't be so sceptical. The main limitations are:

1. Miniaturisation. Obviously this is just an engineering problem. A damn hard one, sure.2. Sampling rate of the light signal. This is the one that will really determine the image quality.

The door requirement is a pretty big limitation though. I think a fibre optic camera poked around the corner might be a bit easier!

I took a look at their supplied graphic and immediatly had a few issues with it. #1 starts with reflection one. Is the door a mirror or is is a surface that will scatter the light into all the room? Same for reflection 2. Think about reflection 2 for a moment. Remember the problem with reflection 1? Which reflection 2? Multiply for reflection 3 and you have no immage, but just a depth sounding ping return from the room with no direction information at all, thus no shape information, only the return ti

Assuming your ambient light isn't coming from a laser wouldn't you be able to get rid of the light by filtering out any non-polarized light? If there are lasers (say multiple people in a SWAT team are using this) as part of the ambient light maybe each could be using a slightly different wavelength of light in order to filter out the other devices as well.

Actually, it sounds like an alternate way of recording a holographic image. The one thing I don't see mentioned is it becomes increasingly more difficult to make this work, the less smooth and flat your reflecting surface gets. In fact, I'd be surprised if this was even feasible if you are reflecting the laser beams off anything that isn't significantly flat and smooth.

The first customer will either be the TSA or some branch of the military.

High-tech companies would invent anything that would sell to any agency vaguely related to counter-terrorism or warfare these days. If they poured a tenth of the resources they spent developing this kind of devices into finding solutions to the world's real problems, we'd all be cancer-free and solar-powered by now...

Funny how impossibilities in science fiction become possible with time. When Star Trek came out in 1966, flat screen monitors, "communicatore", self-opening doors, talking computers, and a lot more stuff that's commonplace now was impossible then.

However, Blade Runner makes the Doctorow Mistake of setting the fiction too close to the present. It's set just ten years from now. It's doubtful this tech will be mature in ten years, and besides, you can't just feed a print into the scanner and see around corners

Depends on the resolution, and of course the refresh rate which determines velocity. Set a 24" monitor to 1x1 resolution with a 100MHz refresh rate, and it hurts like hell. Set it ag 32,700 x 27,000, not so much, unless you get hit by all of the pixels or the pixel you are hit by is at a very high refresh rate.

It is ridiculous to call this new technology. It is just another form range sensing that is being researched in universities all over the world. Light is still just electromagnetic radiation. I am sure there are lots of other projects doing the same this as this, but since it is from the MIT Media Lab it gets the "oooo, awww.." factor.

Using the backscatter from diffuse reflection is seriously limiting.

Radar systems are brutally prone to clutter, echoes, and interference. The system is limited by range, and

This is great. Its an EDM. Surveyors and engineers have been using this technology for half a century, the only difference is they have been excluding these types of measurements deemed reflective inaccuracy. This is a neat idea.

You flash the door. It travels at the speed of light. You get the reflection off the door in twice the distance to the door divided by the speed of light. After that, you open the shutter and start watching.

You then get secondary reflections off the door, as the flash which reflected into the room then reflects off objects in the room, back to the door, and reflects back to you. The intensity of the light reflecting off of the door at any point in time tel

AND they do the same looking at various places on the door, so they see the "distance map" image from various perspectives. This makes it more analogous to the door as a mirror, just as you'd look at various points on a mirror and see a reflected scene from the point of view of that spot on the mirror.

That is, when they have the CSI on TV "enhance the photo, show me the reflection in the car side mirror" In real life, we can not, or rather COULD NOT do that.
But with these special cameras, apparently we will be able to do it.